I think what you may be thinking of near the Four Seasons is the large area of underground walkways in the area near the subway station to the west of the hotel in Marunouchi. They're marked on the local area map I got from the concierge. There seems to be a similar underground area on the north end of Tokyo station. And I'm sure there are similar underground areas in other parts of the city. It isn't hard to walk 1/4 to 1/2 mile here underground!

Anyway - I'm sure it was about 90 or higher today in the mid-afternoon. Definitely not a time you want to be spending hours outside in the sun. Robyn